Garlic has been used for millennia as a culinary herb and foodstuff. Further, many medical properties have been ascribed to garlic and it has been used in folk medicine for thousands of years.
Ajoene is a naturally occurring chemical compound which is derived from garlic. More particularly, ajoene is formed during the degradation of allicin, which is a chemically unstable, colourless to straw coloured oil which is thought to be responsible for much of the odour and biological activity of garlic. An intact garlic clove does not contain allicin but rather its odourless precursor alliin [(+) (S-allyl-L-cysteine sulfoxide)]. This is converted to allicin by a C—S-lyase present in the garlic plant termed alliinase. Alliin and alliinase are found in different compartments of the garlic clove and the cutting or crushing of the clove releases the enzyme allowing it to come into contact with alliin, which is converted to allicin. Allicin is both unstable and volatile, and will naturally degrade principally to diallyl disulphide, diallyl trisulphide, vinyl dithiins and ajoene. A method for preparing allicin in high yield and volume is described in WO-A-2003/004668, the entire contents of which are hereinby incorporated by reference.
Ajoene is presently of interest in a number of fields of endeavour, but predominantly in the medicinal field, including both human and animal pharmaceuticals. However, the study and hence the use of ajoene for such purposes has been curtailed since existing methods for producing ajoene have low selectively for ajoene. Consequently, ajoene is expensive to produce and then only in relatively small yields. For example, U.S. Pat. No. 5,612,077 describes a method using edible oil to produce a macerate containing mainly Z-ajoene but in small volumes and low concentration. U.S. Pat. No. 5,741,932 describes a method of preparing ajoene using cyclodextrin which is a complicated multi step method and which again produces small volumes at a low concentration.
Further, much of the previous research on garlic and its potential uses has not been specific about the active agent, which is typically referred to as ‘a garlic extract’ or ‘garlic oil’.
Thus, there is a need for an improved process for obtaining ajoene in high yield, in high volumes, and at reasonable cost. There is also a need for an improved process for obtaining allicin, a precursor to ajoene, in high yield, in high volumes, and at reasonable cost.